Load-carrying skeletal members, such as the human hip, frequently are rendered non-functional because of fracture, damage, disease, resections for malignancy or disease, pain or malformation. Such members are commonly repaired by a total joint replacement with artificial components, and one type of bone replacement that has been particularly common over the past number of years is that of the human hip. Such hip prostheses typically include a femoral portion or component which is implanted in the femur and an acetabular component which is secured to the pelvis. The femoral component includes a head which rotates in a socket formed in the acetabular component and a stemmed portion which extends into the medullary canal of the femur bone. The head is connected to the stemmed portion by a narrowed, neck portion and a collar is often provided on the stemmed portion which rests in contact with the proximal end of the femur. This femoral head may be permanently secured to or formed integrally with the stemmed portion or the femoral head may be removable from the stemmed portion. Examples of such prostheses are illustrated in the following U.S. Pat. Nos. 4,459,708; 4,406,023; 3,938,198; 3,228,393; 4,038,703; 3,740,769; 3,744,061; 4,012,796; 4,146,936; 4,156,943; 3,808,606; 3,102,536; and 4,080,666. In addition, the following foreign patents disclose known prostheses: German Patent No. 3,003,050; German Patent No. 2,914,454; and British Patent No. 1,446,097.
Many of these known prosthetic devices require the use of cement for embedding the stemmed portion of the femoral component into the medullary canal of the femur. While known cemented systems usually are satisfactory in the short term, various reports of long term results of cemented total hip replacements with a minimum follow up of ten years show that the loosening rate of the femoral component is in the neighborhood of 30% to 50%. (See Moreland, J. R., et al, "Aseptic Loosening of Total Hip Replacement: Incidence and Significance" In the Hip: Proceedings of the Eighth Open Scientific Meeting of the Hip Society, pp. 281-291, St. Louis, C. V. Mosby, 1980); Salvatti, E. A., et al, "A Ten Year Follow-Up Study of our First One Hundred Consecutive Charnley Total Hip Replacements", 63 A. J. Bone Joint Surg. 753-767, 1981; Mueller, M. E., "Long Term Follow-Up of Total Hip Replacements", presented at the AOA International Symposium on "Frontiers in Total Hip Replacement", May, 1981, Boston, Mass.; and Coventry, M. B., "Ten Year Follow-Up Study of Total Hip Replacement at the Mayo Clinic", presented at the AOA International Symposium on "Frontiers in Total Hip Replacement", Boston, Mass., May, 1981). Thus, extraction of the femoral component is often required for replacement thereof with a new femoral component.
Because of the problems associated with cemented implants, more recent developments in orthopedic research have been directed toward generating implants which are fixed to the skeleton by bony ingrowth without the use of any cement. Examples of devices utilizing such a bony ingrowth technique are illustrated in U.S. Pat. Nos. 3,314,420; 2,688,139; 3,808,606; and 3,938,198. However, even when bony ingrowth techniques are used, extraction and replacement of the femoral component is often necessary because of changing stresses within the prosthesis and the bone, oversights in the prosthesis design and other factors which may cause dislodgement or premature failure of the implant.
Whether the femoral component is implanted using cement or bony ingrowth techniques, the extraction process is very difficult and dangerous, occasionally resulting in shattering of the femur bone. In some components, such as those illustrated in U.S. Pat. Nos. 4,080,666 and 4,406,023, extraction is facilitated by providing means on the femoral component for attachment of an extractor. Presently, one commonly used method and apparatus for extracting a femoral component is that shown in U.S. Pat. Nos. 4,222,382. U.S. Pat. No. 4,399,813 shows a variation of the apparatus of U.S. Pat. No. 4,222,382 for extracting a broken tip of a femoral component. In the apparatus of U.S. Pat. No. 4,222,382, a sliding weight is utilized to provide an impact shock for breaking the bonds between the component and the bone to allow eventual removal of the component. Forces are applied to the bonds between the component and the bone in a discontinuous manner by the use of a severe jolt or shock. This technique is highly undesirable because of the danger of causing damage to the bone, such as shattering thereof. Another unrelated method of extracting a cemented prosthesis is shown in U.S. Pat. No. 4,248,232.